1. Field of the Invention
The invention relates to an infinitely variable traction roller transmission in which power is transmitted through traction rollers pivotally supported between toric input and output discs.
2. Description of the Related Art
In such transmissions, the traction rollers are mounted on support structures which, when pivoted, cause engagement of the traction rollers with the toric discs in circles of varying diameters depending on the desired transmission ratio. The pivotal traction roller support structures are so supported that they can be moved axially for initiating a change in the transmission ratio. For example, two traction rollers may be supported opposite one another by flexible tension sheets as shown in U.S. Pat. No. 4,086,820 which issued May 2, 1978 to Charles E. Kraus.
In U.S. Pat. No. 4,830,578 by Charles E. Kraus in which two traction rollers are arranged between, and in engagement with, opposite toric traction discs for the transmission of motion therebetween, each traction roller is supported by a pivotal support trunnion which has supported rollers disposed at opposite ends thereof and supported on rollers disposed at opposite ends thereof and supported on partial circular tracks disposed on the housing's rollers are supported on the pivot trunnions by force transmitting means which, for inexpensive transmissions, include stacks of Belleville springs. The housing tracks may have a center of curvature which is slightly off-set with regard to the pivot axis of the trunnions in order to provide greater compression of the Belleville spring, that is, greater disc engagement forces in one pivotal end position of the pivot trunnions than in their opposite pivotal end positions.
The arrangement according to applicant's application Ser. No. 07/259,043 utilizes a single support roller for each trunnion which is received in a partial circular track section mounted in the housing for forcing the trunnion and the associated traction roller into firm engagement with the toric discs for permitting transmission of motion therebetween. An axially projecting control end of each trunnion is supported so as to be slightly movable in a plane normal to the axis of the toric discs, the control ends of the trunnions having means associated therewith for tilting the trunnions in unison in said plane for the initiation of a transmission ratio change.
The roller engagement forces are obtained by wedges adapted to force the track section toward the toric discs so as to generate the engagement forces for the traction rollers with the toric discs.
While this arrangement proved to work very well, it is the object of the present invention to provide a similar arrangement however with simpler means in order to further reduce cost and increase the reliability of such transmissions.